More than 300,000 persons die suddenly each year in the United States due to cardiac arrhythmia (Ventricular tachycardia (VT) and ventricular fibrillation (VF)). Even when these arrhythmias are "controlled" through medication or surgery, annual mortality is still approximately 20%. The Automatic Implantable Cardioverter Defibrillator (AICD) is a new device that is capable of detecting VT/VF and delivering an electrical pulse to the heart so as to restore normal rhythm. Uncontrolled clinical trials indicate that the AICD substantially reduces mortality among persons at high risk of sudden cardiac arrest. However, the device is expensive (the Medicare DRG weight is 7.3) and not all patients adapt psychologically. Optimal patient selection is controversial. We propose a three year project to (1) establish the cost per year of life gained among AICD recipients compared to comparable non-AICD patients; (2) assess the functional status and quality of life among AICD recipients in comparison to similar non-AICD patients, as well as completely different disease states and interventions; (3) prospectively collect cost and patient functional status data on an improved version of the AICD that will soon begin testing; (4) use these and other data to project changes in AICD benefits and cots, given changes in patient selection strategy, broadening of indications for use, and AICD design improvements. There has not been a randomized trial of the AICD. Through collaboration with investigators at the University of Washington who are conducting long-term followup studies of cardiac arrest survivors, we will form a reference group of persons comparable to those who received an AICD at our institution. Design of the investigation is based on comparisons between these AICD and non- AICD groups. Results will: (1) establish the survival value of the AICD, and its marginal benefit versus marginal cost; (2) described quality of life among AICD recipients; (3) project the effect on AICD costs and benefits of specific chances in patient selection and design of the device; (4) provide a basis for coverage and reimbursement policy.